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      <span class="post-meta-item-icon">
        <i class="far fa-clock"></i>
      </span>
      <span class="post-meta-item-text">阅读时长 &asymp;</span>
      <span>15 分钟</span>
    </span>
</div>

        </div>
      </header>

    
    
    
    <div class="post-body" itemprop="articleBody"><p>本文主要是pinctrl与gpio子系统——gpio子系统相关笔记。若笔记中有错误或者不合适的地方，欢迎批评指正😃。</p>
<span id="more"></span>

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<details class="folding-tag" blue><summary> 点击查看使用工具及版本 </summary>
              <div class='content'>
              <table>    <tr>        <td align="center" width=150px>Windows版本</td>        <td align="left">windows11</td>    </tr>    <tr>        <td align="center">Ubuntu版本</td>        <td align="left">Ubuntu16.04的64位版本</td>      </tr>    <tr>        <td align="center">VMware® Workstation 16 Pro</td>        <td align="left">16.2.3 build-19376536</td>      </tr>    <tr>        <td align="center">终端软件</td>        <td align="left">MobaXterm(Professional Edition v23.0 Build 5042 (license))</td>      </tr>    <tr>        <td align="center">Linux开发板</td>        <td align="left">正点原子 i.MX6ULL Linux 阿尔法开发板</td>      </tr>    <tr>        <td align="center">uboot</td>        <td align="left">NXP官方提供的uboot，NXP提供的版本为uboot-imx-rel_imx_4.1.15_2.1.0_ga(使用的uboot版本为U-Boot 2016.03)</td>      </tr>    <tr>        <td align="center">linux内核</td>        <td align="left">linux-4.15(NXP官方提供)</td>      </tr>    <tr>        <td align="center">Win32DiskImager</td>        <td align="left">Win32DiskImager v1.0</td>      </tr>    <tr>        <td align="center">buildroot</td>        <td align="left">2023.05.1版本</td>      </tr></table>
              </div>
            </details>

<details class="folding-tag" blue><summary> 点击查看本文参考资料 </summary>
              <div class='content'>
              <table>    <tr>        <td align="center">分类</td>        <td align="center">网址</td>        <td align="center">说明</td>    </tr>    <tr>        <td align="center" rowspan="5">官方网站</td>        <td align="left"><a href="https://www.arm.com/" target="_blank">https://www.arm.com/</a></td>        <td align="left">ARM官方网站，在这里我们可以找到Cotex-Mx以及ARMVx的一些文档</td>    </tr>    <tr>        <td align="left"><a href="https://www.nxp.com.cn/" target="_blank">https://www.nxp.com.cn/ </a></td>        <td align="left">NXP官方网站</td>    </tr>    <tr>        <td align="left"><a href="https://www.nxpic.org.cn/" target="_blank">https://www.nxpic.org.cn/</a></td><td align="left">NXP 官方社区</td>    </tr>    <tr>        <td align="left"><a href="https://u-boot.readthedocs.io/en/latest/" target="_blank">https://u-boot.readthedocs.io/en/latest/</a></td><td align="left">u-boot官网</td>    </tr>    <tr>        <td align="left"><a href="https://www.kernel.org/" target="_blank">https://www.kernel.org/</a></td><td align="left">linux内核官网</td>    </tr></table>
              </div>
            </details>

<details class="folding-tag" blue><summary> 点击查看相关文件下载 </summary>
              <div class='content'>
              <table>    <tr>        <td align="center">分类</td>        <td align="center">网址</td>        <td align="center">说明</td>    </tr>    <tr>        <td align="center" rowspan="4">NXP</td>        <td align="left"><a href="https://github.com/nxp-imx" target="_blank">https://github.com/nxp-imx</a></td>        <td align="left">NXP imx开发资源GitHub组织，里边会有u-boot和linux内核的仓库</td>    </tr>    <tr>        <td align="left"><a href="https://elixir.bootlin.com/linux/latest/source" target="_blank">https://elixir.bootlin.com/linux/latest/source</a></td>        <td align="left">在线阅读linux kernel源码</td>    </tr>    <tr>        <td align="left"><a href="https://github.com/nxp-imx/linux-imx/releases/tag/rel_imx_4.1.15_2.1.0_ga" target="_blank">nxp-imx/linux-imx/releases/tag/rel_imx_4.1.15_2.1.0_ga</a></td>        <td align="left">NXP linux内核仓库tags中的rel_imx_4.1.15_2.1.0_ga</td>    </tr>    <tr>        <td align="left"><a href="https://github.com/nxp-imx/uboot-imx/releases/tag/rel_imx_4.1.15_2.1.0_ga" target="_blank">nxp-imx/uboot-imx/releases/tag/rel_imx_4.1.15_2.1.0_ga</a></td>        <td align="left">NXP u-boot仓库tags中的rel_imx_4.1.15_2.1.0_ga</td>    </tr>    <tr>        <td align="center" rowspan="2">I.MX6ULL</td>        <td align="left"><a href="https://www.nxp.com.cn/docs/en/data-sheet/IMX6ULLIEC.pdf" target="_blank">i.MX 6ULL Applications Processors for Industrial Products</a></td>        <td align="left">I.MX6ULL 芯片手册（datasheet，可以在线查看）</td>    </tr>    <tr>        <td align="left"><a href="https://www.nxp.com.cn/webapp/Download?colCode=IMX6ULLRM&lang_cd=zh" target="_blank">i.MX 6ULL Applications ProcessorReference Manual</a></td>        <td align="left">I.MX6ULL 参考手册（下载后才能查看，需要登录NXP官网）</td>    </tr></table>
              </div>
            </details>

<h1 id="一、概述"><a href="#一、概述" class="headerlink" title="一、概述"></a><font size=3>一、概述</font></h1><p>pinctrl 子系统重点是设置 PIN(有的 SOC 叫做 PAD)的复用和电气属性，如果 pinctrl 子系统将一个 PIN 复用为 GPIO 的话，那么接下来就要用到 gpio 子系统了。 </p>
<p>gpio 子系统顾名思义，就是用于初始化 GPIO 并且提供相应的 API 函数，比如设置 GPIO为输入输出，读取 GPIO 的值等。 gpio 子系统的主要目的就是方便驱动开发者使用 gpio，驱动开发者在设备树中添加 gpio 相关信息，然后就可以在驱动程序中使用 gpio 子系统提供的 API函数来操作 GPIO， Linux 内核向驱动开发者屏蔽掉了 GPIO 的设置过程，极大的方便了驱动开发者使用 GPIO。  </p>
<h1 id="二、I-MX6ULL-的-gpio-子系统驱动"><a href="#二、I-MX6ULL-的-gpio-子系统驱动" class="headerlink" title="二、I.MX6ULL 的 gpio 子系统驱动  "></a><font size=3>二、I.MX6ULL 的 gpio 子系统驱动  </font></h1><h2 id="1-设备树中的-gpio-信息"><a href="#1-设备树中的-gpio-信息" class="headerlink" title="1. 设备树中的 gpio 信息  "></a><font size=3>1. 设备树中的 gpio 信息  </font></h2><p>I.MX6ULL-ALPHA 开发板上的 UART1_RTS_B 做为 SD 卡的检测引脚， UART1_RTS_B 复用为 GPIO1_IO19，通过读取这个 GPIO 的高低电平就可以知道 SD 卡有没有插入。首先肯定是将 UART1_RTS_B 这个 PIN 复用为 GPIO1_IO19，并且设置电气属性，也就是上一小节学习的pinctrl 节点。打开 imx6ull-alpha-emmc.dts， UART1_RTS_B 这个 PIN 的 pincrtl 设置如下：  </p>
<img data-src="https://fanhua-picture.oss-cn-hangzhou.aliyuncs.com/01%E5%B5%8C%E5%85%A5%E5%BC%8F%E5%BC%80%E5%8F%91/02IMX6ULL%E5%B9%B3%E5%8F%B0/LV06-%E9%A9%B1%E5%8A%A8%E5%BC%80%E5%8F%91/LV06-02-%E5%AD%97%E7%AC%A6%E8%AE%BE%E5%A4%87%E9%A9%B1%E5%8A%A8-01-pinctrl%E4%B8%8Egpio%E5%AD%90%E7%B3%BB%E7%BB%9F-02-gpio/img/image-20230826160108109.png" alt="image-20230826160108109" style="zoom:50%;" />

<p>pinctrl 配置好以后就是设置 gpio 了， SD 卡驱动程序通过读取 GPIO1_IO19 的值来判断 SD卡有没有插入，但是 SD 卡驱动程序怎么知道 CD 引脚连接的 GPIO1_IO19 呢？肯定是需要设备树告诉驱动啊！在设备树中 SD 卡节点下添加一个属性来描述 SD 卡的 CD 引脚就行了， SD卡驱动直接读取这个属性值就知道 SD 卡的 CD 引脚使用的是哪个 GPIO 了。 SD 卡连接在I.MX6ULL 的 usdhc1 接口上，在 imx6ull-alpha-emmc.dts 中找到名为“usdhc1”的节点，这个节点就是 SD 卡设备节点，如下所示  </p>
<img data-src="https://fanhua-picture.oss-cn-hangzhou.aliyuncs.com/01%E5%B5%8C%E5%85%A5%E5%BC%8F%E5%BC%80%E5%8F%91/02IMX6ULL%E5%B9%B3%E5%8F%B0/LV06-%E9%A9%B1%E5%8A%A8%E5%BC%80%E5%8F%91/LV06-02-%E5%AD%97%E7%AC%A6%E8%AE%BE%E5%A4%87%E9%A9%B1%E5%8A%A8-01-pinctrl%E4%B8%8Egpio%E5%AD%90%E7%B3%BB%E7%BB%9F-02-gpio/img/image-20230826160435363.png" alt="image-20230826160435363" style="zoom:50%;" />

<p>第 757 行，此行本来没有，是添加的注释信息， usdhc1 节点作为 SD 卡设备总节点， usdhc1 节点需要描述 SD 卡所有的信息，因为驱动要使用。本行就是描述 SD 卡的 CD 引脚 pinctrl 信息所在的子节点，因为 SD 卡驱动需要根据 pincrtl 节点信息来设置 CD 引脚的复用功能等。754~756行的 pinctrl-0~2 都是 SD 卡其他 PIN 的 pincrtl 节点信息。但是会发现，其实在 usdhc1 节点中并没有“pinctrl-3 &#x3D; &lt;&amp;pinctrl_hog_1&gt;”这一行，也就是说并没有指定CD 引脚的 pinctrl 信息，那么 SD 卡驱动就没法设置 CD 引脚的复用功能啊？这个不用担心，因为在“iomuxc”节点下引用了 pinctrl_hog_1 这个节点，所以Linux 内核中的 iomuxc 驱动就会自动初始化 pinctrl_hog_1节点下的所有 PIN。</p>
<p>第 758 行，属性“cd-gpios”描述了 SD 卡的 CD 引脚使用的哪个 IO。属性值一共有三个，我们来看一下这三个属性值的含义，“&amp;gpio1”表示 CD 引脚所使用的 IO 属于 GPIO1 组，“19” 表示 GPIO1 组的第 19 号 IO，通过这两个值 SD 卡驱动程序就知道 CD 引脚使用了 GPIO1_IO19这GPIO。 “ GPIO_ACTIVE_LOW ” 表示低电平有效，如果改为“GPIO_ACTIVE_HIGH”就表示高电平有效。  </p>
<p>根据上面这些信息， SD 卡驱动程序就可以使用 GPIO1_IO19 来检测 SD 卡的 CD 信号了，打开 imx6ull.dtsi，在里面找到如下所示内容 ：</p>
<img data-src="https://fanhua-picture.oss-cn-hangzhou.aliyuncs.com/01%E5%B5%8C%E5%85%A5%E5%BC%8F%E5%BC%80%E5%8F%91/02IMX6ULL%E5%B9%B3%E5%8F%B0/LV06-%E9%A9%B1%E5%8A%A8%E5%BC%80%E5%8F%91/LV06-02-%E5%AD%97%E7%AC%A6%E8%AE%BE%E5%A4%87%E9%A9%B1%E5%8A%A8-01-pinctrl%E4%B8%8Egpio%E5%AD%90%E7%B3%BB%E7%BB%9F-02-gpio/img/image-20230826160832206.png" alt="image-20230826160832206" style="zoom:50%;" />

<p>gpio1 节点信息描述了 GPIO1 控制器的所有信息，重点就是 GPIO1 外设寄存器基地址以及兼容属性 。关于I.MX 系列 SOC 的GPIO控制器绑定信息可以查看 文档 Documentation&#x2F;devicetree&#x2F;bindings&#x2F;gpio&#x2F; fsl-imx-gpio.txt。  </p>
<p>第 505 行，设置 gpio1 节点的 compatible 属性有两个，分别为“fsl,imx6ul-gpio”和“fsl,imx35-gpio”，在 Linux 内核中搜索这两个字符串就可以找到 I.MX6UL 的 GPIO 驱动程序。</p>
<p>第 506 行， reg 属性设置了 GPIO1 控制器的寄存器基地址为 0X0209C000，可以打开《I.MX6ULL 参考手册》找到“Chapter 28:General Purpose Input&#x2F;Output(GPIO)”章节第 28.5 小节，有如图所示的寄存器地址表：  </p>
<img data-src="https://fanhua-picture.oss-cn-hangzhou.aliyuncs.com/01%E5%B5%8C%E5%85%A5%E5%BC%8F%E5%BC%80%E5%8F%91/02IMX6ULL%E5%B9%B3%E5%8F%B0/LV06-%E9%A9%B1%E5%8A%A8%E5%BC%80%E5%8F%91/LV06-02-%E5%AD%97%E7%AC%A6%E8%AE%BE%E5%A4%87%E9%A9%B1%E5%8A%A8-01-pinctrl%E4%B8%8Egpio%E5%AD%90%E7%B3%BB%E7%BB%9F-02-gpio/img/image-20230826161019216.png" alt="image-20230826161019216" style="zoom:50%;" />

<p>可以看出， GPIO1 控制器的基地址就是 0X0209C000。</p>
<p>第 509 行，“gpio-controller”表示 gpio1 节点是个 GPIO 控制器。</p>
<p>第 510 行，“#gpio-cells”属性和“#address-cells”类似， #gpio-cells 应该为 2，表示一共有两个 cell，第一个 cell 为 GPIO 编号，比如“&amp;gpio1 3”就表示 GPIO1_IO03。第二个 cell 表示GPIO 极 性 ， 如 果 为 0(GPIO_ACTIVE_HIGH) 的 话表示高电平有效，如果为1(GPIO_ACTIVE_LOW)的话表示低电平有效。  </p>
<h2 id="2-GPIO-驱动程序"><a href="#2-GPIO-驱动程序" class="headerlink" title="2. GPIO 驱动程序  "></a><font size=3>2. GPIO 驱动程序  </font></h2><p>gpio1 节点的 compatible 属性描述了兼容性，在 Linux 内核中搜索“fsl,imx6ul-gpio”和“fsl,imx35-gpio”这两个字符串，查找 GPIO 驱动文件。 drivers&#x2F;gpio&#x2F;gpio-mxc.c 就是 I.MX6ULL的 GPIO 驱动文件，在此文件中有如下所示 of_device_id 匹配表：  </p>
<img data-src="https://fanhua-picture.oss-cn-hangzhou.aliyuncs.com/01%E5%B5%8C%E5%85%A5%E5%BC%8F%E5%BC%80%E5%8F%91/02IMX6ULL%E5%B9%B3%E5%8F%B0/LV06-%E9%A9%B1%E5%8A%A8%E5%BC%80%E5%8F%91/LV06-02-%E5%AD%97%E7%AC%A6%E8%AE%BE%E5%A4%87%E9%A9%B1%E5%8A%A8-01-pinctrl%E4%B8%8Egpio%E5%AD%90%E7%B3%BB%E7%BB%9F-02-gpio/img/image-20230826161256859.png" alt="image-20230826161256859" style="zoom:50%;" />

<p>第 156 行的 compatible 值为“fsl,imx35-gpio”，和 gpio1 的 compatible 属性匹配，因此 gpiomxc.c 就是 I.MX6ULL 的 GPIO 控制器驱动文件。 gpio-mxc.c 所在的目录为 drivers&#x2F;gpio，打开这个目录可以看到很多芯片的 gpio 驱动文件， “gpiolib”开始的文件是 gpio 驱动的核心文件：  </p>
<img data-src="https://fanhua-picture.oss-cn-hangzhou.aliyuncs.com/01%E5%B5%8C%E5%85%A5%E5%BC%8F%E5%BC%80%E5%8F%91/02IMX6ULL%E5%B9%B3%E5%8F%B0/LV06-%E9%A9%B1%E5%8A%A8%E5%BC%80%E5%8F%91/LV06-02-%E5%AD%97%E7%AC%A6%E8%AE%BE%E5%A4%87%E9%A9%B1%E5%8A%A8-01-pinctrl%E4%B8%8Egpio%E5%AD%90%E7%B3%BB%E7%BB%9F-02-gpio/img/image-20230826161420932.png" alt="image-20230826161420932" style="zoom:50%;" />

<p>我们重点来看一下 gpio-mxc.c 这个文件，在 gpio-mxc.c 文件中有如下所示内容 ：</p>
<img data-src="https://fanhua-picture.oss-cn-hangzhou.aliyuncs.com/01%E5%B5%8C%E5%85%A5%E5%BC%8F%E5%BC%80%E5%8F%91/02IMX6ULL%E5%B9%B3%E5%8F%B0/LV06-%E9%A9%B1%E5%8A%A8%E5%BC%80%E5%8F%91/LV06-02-%E5%AD%97%E7%AC%A6%E8%AE%BE%E5%A4%87%E9%A9%B1%E5%8A%A8-01-pinctrl%E4%B8%8Egpio%E5%AD%90%E7%B3%BB%E7%BB%9F-02-gpio/img/image-20230826161554787.png" alt="image-20230826161554787" style="zoom:50%;" />

<p>可以看出 GPIO 驱动也是个平台设备驱动，因此当设备树中的设备节点与驱动的of_device_id 匹配以后 probe 函数就会执行，在这里就是 mxc_gpio_probe 函数，这个函数就是I.MX6ULL 的 GPIO 驱动入口函数。  这里就不详细分析了，流程都跟platform平台总线驱动类似。</p>
<h1 id="三、gpio-子系统-API-函数"><a href="#三、gpio-子系统-API-函数" class="headerlink" title="三、gpio 子系统 API 函数  "></a><font size=3>三、gpio 子系统 API 函数  </font></h1><h2 id="1-gpio-request"><a href="#1-gpio-request" class="headerlink" title="1. gpio_request()"></a><font size=3>1. gpio_request()</font></h2><figure class="highlight c"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br></pre></td><td class="code"><pre><span class="line"><span class="comment">/* 函数声明 */</span></span><br><span class="line"><span class="type">int</span> <span class="title function_">gpio_request</span><span class="params">(<span class="type">unsigned</span> gpio, <span class="type">const</span> <span class="type">char</span> *label)</span>;</span><br></pre></td></tr></table></figure>

<p><strong>【函数说明】</strong>该函数用于申请一个 GPIO 管脚，在使用一个 GPIO 之前一定要使用 gpio_request进行申请  。</p>
<p><strong>【函数参数】</strong></p>
<ul>
<li>gpio：要申请的 gpio 标号，使用 of_get_named_gpio 函数从设备树获取指定 GPIO 属性信息，此函数会返回这个 GPIO 的标号。 </li>
<li>label：给 gpio 设置个名字 。</li>
</ul>
<p><strong>【返回值】</strong> int 类型，0，申请成功；其他值，申请失败。  </p>
<p><strong>【使用格式】</strong>none</p>
<p><strong>【注意事项】</strong> none </p>
<h2 id="2-gpio-free"><a href="#2-gpio-free" class="headerlink" title="2. gpio_free()"></a><font size=3>2. gpio_free()</font></h2><figure class="highlight c"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br></pre></td><td class="code"><pre><span class="line"><span class="comment">/* 函数声明 */</span></span><br><span class="line"><span class="type">void</span> <span class="title function_">gpio_free</span><span class="params">(<span class="type">unsigned</span> gpio)</span>;</span><br></pre></td></tr></table></figure>

<p><strong>【函数说明】</strong>如果不使用某个 GPIO 了，那么就可以调用 gpio_free 函数进行释放  </p>
<p><strong>【函数参数】</strong></p>
<ul>
<li>gpio：要释放的 gpio 标号。</li>
</ul>
<p><strong>【返回值】</strong> none</p>
<p><strong>【使用格式】</strong>none</p>
<p><strong>【注意事项】</strong> none </p>
<h2 id="3-gpio-direction-input"><a href="#3-gpio-direction-input" class="headerlink" title="3. gpio_direction_input  ()"></a><font size=3>3. gpio_direction_input  ()</font></h2><figure class="highlight c"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br></pre></td><td class="code"><pre><span class="line"><span class="comment">/* 函数声明 */</span></span><br><span class="line"><span class="type">int</span> <span class="title function_">gpio_direction_input</span><span class="params">(<span class="type">unsigned</span> gpio)</span>;</span><br></pre></td></tr></table></figure>

<p><strong>【函数说明】</strong>该函数用于设置某个 GPIO 为输入  。</p>
<p><strong>【函数参数】</strong></p>
<ul>
<li>gpio：要设置为输入的 GPIO 标号。</li>
</ul>
<p><strong>【返回值】</strong> int 类型，0，设置成功；负值，设置失败。  </p>
<p><strong>【使用格式】</strong>none</p>
<p><strong>【注意事项】</strong> none </p>
<h2 id="4-gpio-direction-output"><a href="#4-gpio-direction-output" class="headerlink" title="4. gpio_direction_output  ()"></a><font size=3>4. gpio_direction_output  ()</font></h2><figure class="highlight c"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br></pre></td><td class="code"><pre><span class="line"><span class="comment">/* 函数声明 */</span></span><br><span class="line"><span class="type">int</span> <span class="title function_">gpio_direction_output</span><span class="params">(<span class="type">unsigned</span> gpio, <span class="type">int</span> value)</span>;</span><br></pre></td></tr></table></figure>

<p><strong>【函数说明】</strong>该函数用于设置某个 GPIO 为输出，并且设置默认输出值。</p>
<p><strong>【函数参数】</strong></p>
<ul>
<li>gpio：要设置为输出的 GPIO 标号。  </li>
<li>value： GPIO 默认输出值。</li>
</ul>
<p><strong>【返回值】</strong> int 类型，0，设置成功；负值，设置失败。  </p>
<p><strong>【使用格式】</strong>none</p>
<p><strong>【注意事项】</strong> none </p>
<h2 id="5-gpio-get-value"><a href="#5-gpio-get-value" class="headerlink" title="5. gpio_get_value  ()"></a><font size=3>5. gpio_get_value  ()</font></h2><figure class="highlight c"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br></pre></td><td class="code"><pre><span class="line"><span class="comment">/* 函数声明 */</span></span><br><span class="line"><span class="meta">#<span class="keyword">define</span> gpio_get_value __gpio_get_value</span></span><br><span class="line"><span class="type">int</span> __gpio_get_value(<span class="type">unsigned</span> gpio);</span><br></pre></td></tr></table></figure>

<p><strong>【函数说明】</strong>该函数用于获取某个 GPIO 的值(0 或 1)，此函数是个宏。</p>
<p><strong>【函数参数】</strong></p>
<ul>
<li>gpio：要获取的 GPIO 标号。</li>
</ul>
<p><strong>【返回值】</strong> int 类型，非负值，得到的 GPIO 值；负值，获取失败。</p>
<p><strong>【使用格式】</strong>none</p>
<p><strong>【注意事项】</strong> none </p>
<h2 id="6-gpio-set-value"><a href="#6-gpio-set-value" class="headerlink" title="6. gpio_set_value  ()"></a><font size=3>6. gpio_set_value  ()</font></h2><figure class="highlight c"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br></pre></td><td class="code"><pre><span class="line"><span class="comment">/* 函数声明 */</span></span><br><span class="line"><span class="meta">#<span class="keyword">define</span> gpio_set_value __gpio_set_value</span></span><br><span class="line"><span class="type">void</span> __gpio_set_value(<span class="type">unsigned</span> gpio, <span class="type">int</span> value);</span><br></pre></td></tr></table></figure>

<p><strong>【函数说明】</strong>该函数用于设置某个 GPIO 的值，此函数是个宏。</p>
<p><strong>【函数参数】</strong></p>
<ul>
<li>gpio：要设置的 GPIO 标号。</li>
<li>value： 要设置的值。</li>
</ul>
<p><strong>【返回值】</strong> none</p>
<p><strong>【使用格式】</strong>none</p>
<p><strong>【注意事项】</strong> none </p>
<h1 id="四、设备树中添加-gpio-节点模板"><a href="#四、设备树中添加-gpio-节点模板" class="headerlink" title="四、设备树中添加 gpio 节点模板  "></a><font size=3>四、设备树中添加 gpio 节点模板  </font></h1><p>前边我们了解了如何创建 test 设备的 pinctrl 节点。现在我们来学习一下如何创建 test 设备的 GPIO 节点。  </p>
<h2 id="1-创建-test-设备节点"><a href="#1-创建-test-设备节点" class="headerlink" title="1. 创建 test 设备节点  "></a><font size=3>1. 创建 test 设备节点  </font></h2><p>在根节点“&#x2F;”下创建 test 设备子节点，如下所示：  </p>
<figure class="highlight c"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br></pre></td><td class="code"><pre><span class="line">test &#123;</span><br><span class="line">	<span class="comment">/* 节点内容 */</span></span><br><span class="line">&#125;;</span><br></pre></td></tr></table></figure>

<h2 id="2-添加-pinctrl-信息"><a href="#2-添加-pinctrl-信息" class="headerlink" title="2. 添加 pinctrl 信息  "></a><font size=3>2. 添加 pinctrl 信息  </font></h2><p>前边我们创建了 pinctrl_test 节点，此节点描述了 test 设备所使用的 GPIO1_IO00 这个 PIN 的信息，我们要将这节点添加到 test 设备节点中，如下所示：  </p>
<figure class="highlight c"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br></pre></td><td class="code"><pre><span class="line">test &#123;</span><br><span class="line">	pinctrl-names = <span class="string">&quot;default&quot;</span>;</span><br><span class="line">	pinctrl<span class="number">-0</span> = &lt;&amp;pinctrl_test&gt;;</span><br><span class="line">	<span class="comment">/* 其他节点内容 */</span></span><br><span class="line">&#125;;</span><br></pre></td></tr></table></figure>

<p>第 2 行，添加 pinctrl-names 属性，此属性描述 pinctrl 名字为“default”。</p>
<p>第 3 行，添加 pinctrl-0 节点，此节点引用之前创建的 pinctrl_test 节点，表示 tset 设备的所使用的 PIN 信息保存在 pinctrl_test 节点中。  </p>
<h2 id="3-添加-GPIO-属性信息"><a href="#3-添加-GPIO-属性信息" class="headerlink" title="3. 添加 GPIO 属性信息  "></a><font size=3>3. 添加 GPIO 属性信息  </font></h2><p>我们最后需要在 test 节点中添加 GPIO 属性信息，表明 test 所使用的 GPIO 是哪个引脚，添加完成以后如下所示：</p>
<figure class="highlight c"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br></pre></td><td class="code"><pre><span class="line">test &#123;</span><br><span class="line">	pinctrl-names = <span class="string">&quot;default&quot;</span>;</span><br><span class="line">	pinctrl<span class="number">-0</span> = &lt;&amp;pinctrl_test&gt;;</span><br><span class="line">	gpio = &lt;&amp;gpio1 <span class="number">0</span> GPIO_ACTIVE_LOW&gt;;</span><br><span class="line">&#125;;</span><br></pre></td></tr></table></figure>

<p>第 4 行， test 设备所使用的 gpio。</p>
<h2 id="4-与-gpio-相关的-OF-函数"><a href="#4-与-gpio-相关的-OF-函数" class="headerlink" title="4. 与 gpio 相关的 OF 函数  "></a><font size=3>4. 与 gpio 相关的 OF 函数  </font></h2><h3 id="4-1-of-gpio-named-count-函数"><a href="#4-1-of-gpio-named-count-函数" class="headerlink" title="4.1 of_gpio_named_count 函数  "></a><font size=3>4.1 of_gpio_named_count 函数  </font></h3><p>of_gpio_named_count 函数用于获取设备树某个属性里面定义了几个 GPIO 信息，要注意的是空的 GPIO 信息也会被统计到，比如 ：</p>
<figure class="highlight c"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br></pre></td><td class="code"><pre><span class="line">gpios = &lt;<span class="number">0</span></span><br><span class="line">         &amp;gpio1 <span class="number">1</span> <span class="number">2</span></span><br><span class="line">         <span class="number">0</span> &amp;</span><br><span class="line">         gpio2 <span class="number">3</span> <span class="number">4</span>&gt;;</span><br></pre></td></tr></table></figure>

<p>上述代码的“gpios”节点一共定义了 4 个 GPIO，但是有 2 个是空的，没有实际的含义。通过 of_gpio_named_count 函数统计出来的 GPIO 数量就是 4 个，此函数原型如下：  </p>
<figure class="highlight c"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br></pre></td><td class="code"><pre><span class="line"><span class="comment">/* 函数声明 */</span></span><br><span class="line"><span class="type">int</span> <span class="title function_">of_gpio_named_count</span><span class="params">(<span class="keyword">struct</span> device_node *np, <span class="type">const</span> <span class="type">char</span> *propname)</span>;</span><br></pre></td></tr></table></figure>

<p><strong>【函数说明】</strong>该函数用于获取设备树某个属性里面定义了几个 GPIO 信息。</p>
<p><strong>【函数参数】</strong></p>
<ul>
<li>np：设备节点。  </li>
<li>propname：要统计的 GPIO 属性。</li>
</ul>
<p><strong>【返回值】</strong> int类型，正值，统计到的 GPIO 数量；负值，失败。  </p>
<p><strong>【使用格式】</strong>none</p>
<p><strong>【注意事项】</strong> none </p>
<h3 id="4-2-of-gpio-count-函数"><a href="#4-2-of-gpio-count-函数" class="headerlink" title="4.2 of_gpio_count 函数  "></a><font size=3>4.2 of_gpio_count 函数  </font></h3><figure class="highlight c"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br></pre></td><td class="code"><pre><span class="line"><span class="comment">/* 函数声明 */</span></span><br><span class="line"><span class="type">int</span> <span class="title function_">of_gpio_count</span><span class="params">(<span class="keyword">struct</span> device_node *np)</span>;</span><br></pre></td></tr></table></figure>

<p><strong>【函数说明】</strong>该函数和 of_gpio_named_count 函数一样，但是不同的地方在于，此函数统计的是“gpios”这个属性的 GPIO 数量，而 of_gpio_named_count  函数可以统计任意属性的 GPIO 信息。</p>
<p><strong>【函数参数】</strong></p>
<ul>
<li>np：设备节点。</li>
</ul>
<p><strong>【返回值】</strong> int类型，正值，统计到的 GPIO 数量；负值，失败。  </p>
<p><strong>【使用格式】</strong>none</p>
<p><strong>【注意事项】</strong> none </p>
<h3 id="4-3-of-get-named-gpio-函数"><a href="#4-3-of-get-named-gpio-函数" class="headerlink" title="4.3 of_get_named_gpio 函数   "></a><font size=3>4.3 of_get_named_gpio 函数   </font></h3><figure class="highlight c"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br></pre></td><td class="code"><pre><span class="line"><span class="comment">/* 函数声明 */</span></span><br><span class="line"><span class="type">int</span> <span class="title function_">of_get_named_gpio</span><span class="params">(<span class="keyword">struct</span> device_node *np,</span></span><br><span class="line"><span class="params">                      <span class="type">const</span> <span class="type">char</span> *propname,</span></span><br><span class="line"><span class="params">                      <span class="type">int</span> index)</span>;</span><br></pre></td></tr></table></figure>

<p><strong>【函数说明】</strong>该函数获取 GPIO 编号，因为 Linux 内核中关于 GPIO 的 API 函数都要使用 GPIO 编号，此函数会将设备树中类似&lt;&amp;gpio5 7 GPIO_ACTIVE_LOW&gt;的属性信息转换为对应的 GPIO 编号。</p>
<p><strong>【函数参数】</strong></p>
<ul>
<li>np：设备节点。  </li>
<li>propname：包含要获取 GPIO 信息的属性名。  </li>
<li>index： GPIO 索引，因为一个属性里面可能包含多个 GPIO，此参数指定要获取哪个 GPIO的编号，如果只有一个 GPIO 信息的话此参数为 0。</li>
</ul>
<p><strong>【返回值】</strong> int类型，正值，获取到的 GPIO 编号；负值，失败。  </p>
<p><strong>【使用格式】</strong>none</p>
<p><strong>【注意事项】</strong> none </p>

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